At present, in the existing digital film projector, a display screen is typically set up to display the relevant information from the projector, for example, the films to be played, the playing operations and relevant parameters in the film playing process etc. The display screen is usually connected by a control circuit to a storage unit in the projector, and it is usually operated by an operator.
With the popularization of digital film entertainment, the second-tier market and its additional requirements for digital film playback have emerged. For example, private cinema viewers are eager to adopt professional digital film players so as to enjoy first-run theatrical film releases at the comfort of their own homes; further, there are some personalized demands in the film market, such as ordering and watching of a particular post theatrical film when desired. These services are usually provided in a movie premiere, a party, or as part of some commercial activity. In addition, the demands for watching first-run and post-theatrical film releases call for a system that is capable of charging on a play-count. However, existing digital film projection systems cannot meet the requirements and demands of this second-tier market due to their inherent limitations of obtaining authorization from digital film playback.
Some of the reasons are as follows.
For copyright protection, existing cinema projection systems usually adopt a KDM (Key Delivery Message) licensing method, which means that a cinema needs to apply for a KDM from a film distributor. The KDM is a file for delivering a key; it mainly contains the following three kinds of information: a content decryption key, a key parameter and a TDL (Trusted Device List). The key parameter is mainly the key's time window (valid time period), i.e., the scheduled time for playing a film. The TDL is an information list of the valid and authorized equipment to play the film.
The encrypted film content and its key are generated after a digital film is compressed, encrypted and packaged. The encrypted film content and its relevant information form a Digital Cinema Package (DCP), and are transmitted to an exhibitor or a cinema; the key, upon being further encrypted, will be digitally signed along with other relevant information to form a KDM, and is then transmitted to authorized cinemas by a film distributor or its entrusted film producer. Upon receiving the KDM, the cinema can decrypt and play the encrypted digital film only by correctly extracting the film content and obtaining the key after decryption. In addition to the key, the KDM also includes the valid time period and a TDL for the key etc. Therefore, by virtue of such information, the film distributor can control both the film playing schedule and the projector. In other words, a film cannot be played if the time period carried by the KDM is exceeded, or if it is in a projector not in connection with the server designated by the KDM.
The key's time window is determined upon communications among the film distributor, the cinema and the film producer. After the key has expired, the cinema can apply for an extension if necessary. After the application for extension is approved, the key must be reproduced, and the film distributor (e.g. The China Film Group in mainland China) issues a “Notice of Extension” on its official website and indicates the expiration date of the extended key.
The aforementioned KDM distribution method is defined as part of the Digital Cinema Initiative (DCI) standard, and the KDM format cannot be altered arbitrarily. At present, digital film projection technology can be broadly categorized on the basis of resolution ratio, namely into 4K, 2K, 1.3K and 0.8K. 4K (resolution ratio of 4096×2016 8.25 megapixel) projection is currently the state-of-the-art for commercial digital projection, and it is not commonly adopted even in major cinema networks in first-tier cities. 2K (resolution ratio of 2048×1080 2.21 megapixel) is currently the international standard for film projection. 2K is effectively the same as 4K in terms of synchronized film playing, as the difference of the visual effects between 2K and 4K can only be seen on a display screen of more than 20 m in width. 1.3K (a resolution ratio of 1280×1024 1.31 megapixel) is the current Chinese National standard, whereas 0.8K (resolution ratio of 1024×768 0.786 megapixel) is a film projection standard used mainly in rural China. Overall, there is a wide adoption of various projection standards across China.
Due to copyright restrictions, digital films, when exhibited in cinemas, have to be played on specialized hardware, such as a dedicated chip in the server of a digital film projector, using a specialized process such as the abovementioned KDM method for playing digital films to manage the playable time, the authorized server information, and the key used for decrypting a film for playing. However, at present, the KDM can only control the playable time period, which is appropriate for commercial cinemas due to their fixed daily schedule for playback of digital films. However, this is unsuitable for the purposes of secondary markets such as private cinemas. In addition, post-theatrical release films (in abovementioned DCP formats) cannot be played on-demand. Unlike a film in its theatrical release, the requirements for playing a film after theatrical release are not as high. Accordingly, subsequent distribution is difficult, and on-demand requirements are not met. Based on the prior art, digital films cannot be played under the control of play-count in the second-tier market in private cinemas during and after theatrical release.
Therefore, the prior art needs to be improved and developed.